Efficient single-pixel imaging based on a compact fiber laser array and untrained neural network.

This paper presents an efficient scheme for single-pixel imaging (SPI) utilizing a phase-controlled fiber laser array and an untrained deep neural network. The fiber lasers are arranged in a compact hexagonal structure and coherently combined to generate illuminating light fields. Through the utilization of high-speed electro-optic modulators in each individual fiber laser module, the randomly modulated fiber laser array enables rapid speckle projection onto the object of interest. Furthermore, the untrained deep neural network is incorporated into the image reconstructing process to enhance the quality of the reconstructed images. Through simulations and experiments, we validate the feasibility of the proposed method and successfully achieve high-quality SPI utilizing the coherent fiber laser array at a sampling ratio of 1.6%. Given its potential for high emitting power and rapid modulation, the SPI scheme based on the fiber laser array holds promise for broad applications in remote sensing and other applicable fields.

The F-box protein RhSAF destabilizes the gibberellic acid receptor RhGID1 to mediate ethylene-induced petal senescence in rose.

Roses are among the most popular ornamental plants cultivated worldwide for their great economic, symbolic, and cultural importance. Nevertheless, rapid petal senescence markedly reduces rose (Rosa hybrida) flower quality and value. Petal senescence is a developmental process tightly regulated by various phytohormones. Ethylene accelerates petal senescence, while gibberellic acid (GA) delays this process. However, the molecular mechanisms underlying the crosstalk between these phytohormones in the regulation of petal senescence remain largely unclear. Here, we identified SENESCENCE-ASSOCIATED F-BOX (RhSAF), an ethylene-induced F-box protein gene encoding a recognition subunit of the SCF-type E3 ligase. We demonstrated that RhSAF promotes degradation of the GA receptor GIBBERELLIN INSENSITIVE DWARF1 (RhGID1) to accelerate petal senescence. Silencing RhSAF expression delays petal senescence, while suppressing RhGID1 expression accelerates petal senescence. RhSAF physically interacts with RhGID1s and targets them for ubiquitin/26S proteasome-mediated degradation. Accordingly, ethylene-induced RhGID1C degradation and RhDELLA3 accumulation are compromised in RhSAF-RNAi lines. Our results demonstrate that ethylene antagonizes GA activity through RhGID1 degradation mediated by the E3 ligase RhSAF. These findings enhance our understanding of the phytohormone crosstalk regulating petal senescence and provide insights for improving flower longevity.

Single-frequency pulsed fiber laser based on an electro-optic modulator with injection seeding technique.

A single-frequency linearly polarization pulsed fiber laser based on an electro-optic modulator with injection seeding technique is demonstrated. The single-frequency performance of the fiber ring-cavity laser is guaranteed by the seed source, which is a distributed-feedback fiber laser based on the π-phase-shifted fiber Bragg grating. The electro-optic modulator triggers active Q-switching of the laser for pulse generation. The devices used in the fiber laser are all polarization-maintaining to ensure linear polarization laser output. Through parameter optimization, the laser generates a single-frequency linearly polarization pulsed laser with a central wavelength of 1064.22 nm, linewidth of 35 MHz, and polarization extinction ratio of better than 40 dB. This type of fiber laser can be applied in lidar, beam combining, nonlinear frequency conversion, and other fields.

Design and implementation of a dual aspheric integrated shaping element for a high-power fiber laser.

A dual aspheric integrated beam shaper suitable for a high-power laser situation has been designed and realized. The model for this lens was derived theoretically and the performance was evaluated using a detailed simulation. The ultrasonic vibration assisted cutting and the high-precision grinding and polishing technology were used for the processing. The surface accuracy was less than 200 nm measured with a profiler, and the roughness was smaller than 20 nm with the help of the white light interferometer. Shaping experiments were carried out, which verified that the Gaussian beam has uniform intensity distribution with a uniformity of 85.13% in the near field and converges to a point in the far field, which is exactly as expected. It thus provides an actual selection for high-power laser shaping.

Ghost imaging based on Fermat spiral laser array designed for remote sensing.

We propose a Fermat spiral laser array as illumination source in ghost imaging. Due to the aperiodic structure, the Fermat spiral laser array generates illuminating light field without spatial periodicity on the normalized second-order intensity correlation function. A single-pixel detector is used to receive the signal light from object for image reconstruction. The effects of laser array parameters on the quality of ghost imaging are analyzed comprehensively. Through experimental demonstration, the Fermat spiral laser array successfully achieves ghost imaging with high quality by combining with the compressive sensing reconstruction algorithm. This method is expected to be applied in remote sensing by combining with phased and collimated fiber laser array equipped with the high emitting power and high-speed modulation frequency.

Generating the 1.5†kW mode-tunable fractional vortex beam by a coherent beam combining system.

As an essential component of the vortex beam, the fractional vortex beam has significantly advanced various applications, such as optical imaging, optical communication, and particle manipulation. However, practical applications face a significant challenge as generating high average power fractional vortex beams remains difficult. Here, we proposed and experimentally demonstrated a high average power mode-tunable fractional vortex beam generator based on an internally sensed coherent beam combining (CBC) system. We presented the first, to the best of our knowledge, successful generation of a 1.5 kW continuous wave fractional vortex beam. Moreover, real-time tuning of the topological charge (TC) from -2/3 to +2/3 was easily achieved using the programmable liquid crystals (LCs). More importantly, the fractional vortex beam copier was presented as well, and the generated fractional vortex beam could be easily transformed into a fractional vortex beam array by changing the fill factor of the laser array. This work can pave the path for the practical implementation of high average power structured light beams.

Numerical simulation of the internal active phase-locking coherent beam combining system.

As a promising way to realize high output power while maintaining high beam quality, coherent beam combining (CBC) of fiber lasers has drawn much interest. Phase control is one of the main technologies to fulfill CBC, which is employed to keep the phases of different fiber lasers consistent. Traditional phase control techniques employ beam splitters after the emitting array to obtain phase mismatch information. Different from the traditional phase-locking technique, the internal phase control technique can obtain phase mismatch information before the laser array output to free space, and the technique is compact and easy to expand to a lager array. In this paper, a CBC system based on an internal phase-locking technique is designed, and relative numerical simulations are studied. By using the cascaded technique, the phase control bandwidth can be greatly increased. The simulation results show that hundreds of laser beams can be effectively combined based on the technique. The results of the numerical simulations can provide significant reference for the compact CBC system design and phase control.

The CALCINEURIN B-LIKE 4/CBL-INTERACTING PROTEIN 3 module degrades repressor JAZ5 during rose petal senescence.

Flower senescence is genetically regulated and developmentally controlled. The phytohormone ethylene induces flower senescence in rose (Rosa hybrida), but the underlying signaling network is not well understood. Given that calcium regulates senescence in animals and plants, we explored the role of calcium in petal senescence. Here, we report that the expression of calcineurin B-like protein 4 (RhCBL4), which encodes a calcium receptor, is induced by senescence and ethylene signaling in rose petals. RhCBL4 interacts with CBL-interacting protein kinase 3 (RhCIPK3), and both positively regulate petal senescence. Furthermore, we determined that RhCIPK3 interacts with the jasmonic acid response repressor jasmonate ZIM-domain 5 (RhJAZ5). RhCIPK3 phosphorylates RhJAZ5 and promotes its degradation in the presence of ethylene. Our results reveal that the RhCBL4-RhCIPK3-RhJAZ5 module mediates ethylene-regulated petal senescence. These findings provide insights into flower senescence, which may facilitate innovations in postharvest technology for extending rose flower longevity.

The ARF2-MYB6 module mediates auxin-regulated petal expansion in rose.

In cut rose (Rosa hybrida), the flower-opening process is closely associated with vase life. Auxin induces the expression of transcription factor genes that function in petal growth via cell expansion. However, the molecular mechanisms underlying the auxin effect during flower opening are not well understood. Here, we identified the auxin-inducible transcription factor gene RhMYB6, whose expression level is high during the early stages of flower opening. Silencing of RhMYB6 delayed flower opening by controlling petal cell expansion through down-regulation of cell expansion-related genes. Furthermore, we demonstrated that the auxin response factor RhARF2 directly interacts with the promoter of RhMYB6 and represses its transcription. Silencing of RhARF2 resulted in larger petal size and delayed petal movement. We also showed that the expression of genes related to ethylene and petal movement showed substantial differences in RhARF2-silenced petals. Our results indicate that auxin-regulated RhARF2 is a critical player that controls flower opening by governing RhMYB6 expression and mediating the crosstalk between auxin and ethylene signaling.

CRISPR/Cas9 Gene Editing of NtAITRs, a Family of Transcription Repressor Genes, Leads to Enhanced Drought Tolerance in Tobacco.

Tobacco is a cash crop throughout the world, and its growth and development are affected by abiotic stresses including drought stress; therefore, drought-tolerant breeding may help to improve tobacco yield and quality under drought stress conditions. Considering that the plant hormone ABA (abscisic acid) is able to regulate plant responses to abiotic stresses via activating ABA response genes, the characterization of ABA response genes may enable the identification of genes that can be used for molecular breeding to improve drought tolerance in tobacco. We report here the identification of NtAITRs (Nicotiana tabacum ABA-induced transcription repressors) as a family of novel regulators of drought tolerance in tobacco. Bioinformatics analysis shows that there are a total of eight NtAITR genes in tobacco, and all the NtAITRs have a partially conserved LxLxL motif at their C-terminus. RT-PCR results show that the expression levels of at least some NtAITRs were increased in response to ABA and drought treatments, and NtAITRs, when recruited to the Gal4 promoter via a fused GD (Gal4 DNA-binding domain), were able to repress transcription activator LD-VP activated expression of the LexA-Gal4-GUS reporter gene. Roles of NtAITRs in regulating drought tolerance in tobacco were analyzed by generating CRISPR/Cas9 gene-edited mutants. A total of three Cas9-free ntaitr12356 quintuple mutants were obtained, and drought treatment assays show that drought tolerance was increased in the ntaitr12356 quintuple mutants. On the other hand, results of seed germination and seedling greening assays show that ABA sensitivity was increased in the ntaitr12356 quintuple mutants, and the expression levels of some ABA signaling key regulator genes were altered in the ntaitr12356-c3 mutant. Taken together, our results suggest that NtAITRs are ABA-responsive genes, and that NtAITRs function as transcription repressors and negatively regulate drought tolerance in tobacco, possibly by affecting plant ABA response via affecting the expression of ABA signaling key regulator genes.

Protein Kinase RhCIPK6 Promotes Petal Senescence in Response to Ethylene in Rose (Rosa Hybrida).

Cultivated roses have the largest global market share among ornamental crops. Postharvest release of ethylene is the main cause of accelerated senescence and decline in rose flower quality. To understand the molecular mechanism of ethylene-induced rose petal senescence, we analyzed the transcriptome of rose petals during natural senescence as well as with ethylene treatment. A large number of differentially expressed genes (DEGs) were observed between developmental senescence and the ethylene-induced process. We identified 1207 upregulated genes in the ethylene-induced senescence process, including 82 transcription factors and 48 protein kinases. Gene Ontology enrichment analysis showed that ethylene-induced senescence was closely related to stress, dehydration, and redox reactions. We identified a calcineurin B-like protein (CBL) interacting protein kinase (CIPK) family gene in Rosa hybrida, RhCIPK6, that was regulated by age and ethylene induction. Reducing RhCIPK6 expression through virus-induced gene silencing significantly delayed petal senescence, indicating that RhCIPK6 mediates petal senescence. In the RhCIPK6-silenced petals, several senescence associated genes (SAGs) and transcription factor genes were downregulated compared with controls. We also determined that RhCIPK6 directly binds calcineurin B-like protein 3 (RhCBL3). Our work thus offers new insights into the function of CIPKs in petal senescence and provides a genetic resource for extending rose vase life.

The R2R3 MYB Transcription Factor MYB71 Regulates Abscisic Acid Response in Arabidopsis.

Abscisic acid (ABA) regulates plant responses to abiotic stresses via regulating the expression of downstream genes, yet the functions of many ABA responsive genes remain unknown. We report here the characterization of MYB71, a R2R3 MYB transcription factor in regulating ABA responses in Arabidopsis. RT-PCR results show that the expression level of MYB71 was increased in response to ABA treatment. Arabidopsis protoplasts transfection results show that MYB71 was specifically localized in nucleus and it activated the Gal4:GUS reporter gene when recruited to the Gal4 promoter by a fused DNA binding domain GD. Roles of MYB71 in regulating plant response to ABA were analyzed by generating Arabidopsis transgenic plants overexpression MYB71 and gene edited mutants of MYB71. The results show that ABA sensitivity was increased in the transgenic plants overexpression MYB71, but decreased in the MYB71 mutants. By using a DEX inducible system, we further identified genes are likely regulated by MYB71, and found that they are enriched in biological process to environmental stimuli including abiotic stresses, suggesting that MYB71 may regulate plant response to abiotic stresses. Taken together, our results suggest that MYB71 is an ABA responsive gene, and MYB71 functions as a transcription activator and it positively regulates ABA response in Arabidopsis.

Cantilevered adaptive fiber-optics collimator based on piezoelectric bimorph actuators.

A novel, to the best of our knowledge, cantilever construction design of an adaptive fiber-optics collimator (AFOC) based on piezoelectric bimorph actuators for tip/tilt control is introduced. With this new cantilever structure, an AFOC with a diameter of only 6 mm was developed, and the output laser beam deviation angle and resonance frequency of the device were measured. The experimental results show that this new AFOC can provide more than 1 mrad deflection angle at a 20 V driving voltage, and the first resonance frequency is about 500 Hz. Further, in order to verify whether the cantilever structure can be used in a high-power fiber collimator, a high-power X-Y positioner with an 8 mm diameter fiber end cap was developed. The experimental results show that the high-power X-Y positioner can output more than 2 kW laser power and provide about 330 µm displacement of the fiber end cap in the X direction and about 770 µm in the Y direction at a 150 V driving voltage.

Internal phase control of coherent fiber laser array without ambiguous phase based on double wavelength detection.

High-power fiber lasers have been widely utilized in manufacturing, medical care, and many other fields. Due to mode instability, nonlinear effects, and so on, the output power of a monolithic fiber laser is limited. Coherent beam combining (CBC) of fiber lasers is a promising way to obtain higher output power. An all-fiber CBC structure with internal phase detection has a compact construction and potential for a larger fiber laser array. For the existing internal active phase control of an all-fiber structure, π phase ambiguity always occurs because of double passing the fiber path. Additional compensation is needed under this condition, and the compactness of the system will decrease. In this paper, internal phase control of an all-fiber structure based on double wavelength detection without π-ambiguity is proposed. By adding a beacon laser with a different wavelength, phase locking of a coherent fiber laser array can be achieved internally without π-ambiguity. A corresponding math model is established, and a phase matched condition is derived. The spectral width of the beacon laser is analyzed, and the result shows that it can reach tens of nanometers with a proper optical path difference. Simulations of seven, 19, and 37 beams are carried out, and the results show that the structure proposed in this paper has the ability to achieve phase control with good robustness. The control bandwidth in the simulation is better than 1 kHz. By properly designing elements, the structure is expected to achieve high-power CBC of an all-fiber structure experimentally.

Distributed active phase-locking of an all-fiber structured laser array by a stochastic parallel gradient descent (SPGD) algorithm.

Coherent beam combining (CBC) of fiber laser array is a promising way to achieve high output power. Phase control is one key point to implement CBC. Appropriate feedback structures should be established to achieve phase control. Most feedback structures of CBC are established after the lasers emit to free space and consist of a set of lenses or mirrors. Those optical elements in free space may hinder array size and integration. In this paper, we demonstrated an all-fiber structured CBC method with distributed phase-locking. By adding an all-fiber measurement loop beside the main laser chain, the phase of main laser chain is appended to the measuring loop. Phases of each main laser chain are locked indirectly though the measurement loops by using stochastic parallel gradient descent (SPGD) algorithm. The principle of distributed phase-locking is also illustrated. Corresponding simulations are carried out and two-channel fiber lasers are coherently combined by this method. The experimental results show that the structure can achieve phase-locking effectively. Stable and distinct interference fringe is observed. Additionally, the structure proposed in this paper is straightforwardly building and expanding.

System design for coherent combined massive fiber laser array based on cascaded internal phase control.

Coherent beam combining (CBC) of a fiber laser can scale the output power while maintaining high beam quality. However, phase detection and control remain a challenge for a high-power CBC system with a massive laser array. This paper provides a novel, to the best of our knowledge, cascaded phase-control technique based on internal phase detection and control, called the cascaded internal phase-control technique. The principle of the technique was introduced in detail, and the numerical simulations were carried out based on the stochastic parallel gradient descent (SPGD) algorithm. The results indicated that the cascaded internal phase-control technique was compatible with the massive laser array. Compared with the traditional CBC based on the SPGD algorithm, the control bandwidth could be improved effectively about seven times (120 steps) than the traditional SPGD algorithm (830 steps). Furthermore, the average root mean square of residual phase error was decreased to 0.03 rad (∼λ/209) with a laser array of 259 channels (7∗37), which was 0.36 rad (∼λ/17) in the traditional SPGD algorithm. In addition, the element expanding capacity was analyzed. Since there is no large-aperture optical device in the phase-detection system, this technique has the advantage of freely designing the caliber of the laser emitting system. This paper could offer a reference for the high-power massive laser array system design and phase control.

Iteration-free, simultaneous correction of piston and tilt distortions in large-scale coherent beam combination systems.

Coherent beam combination (CBC) holds promise for scaling the output power of the laser system while maintaining good beam quality. Owing to the thermal effect and mechanics instability, piston and tilt distortions always exist and affect the performance of the combined beam. To ensure the constructive interference in the far-field, dynamic correction of the distortions is highly required. Here, we propose an approach for the simultaneous correction of piston and tilt distortions in CBC systems. Based on the position and interval information of the near-field interference fringes, the theoretical expressions for the relative piston phase and tilt errors of each array element are derived, indicating that dynamic distortions in CBC systems can be directly calculated and then corrected by employing phase control servos. To demonstrate the feasibility of the proposed approach, Monte-Carlo Simulations have been carried out for different perturbative environments. Our results indicate that both piston phase and tilt errors can be calculated and compensated accurately (λ/25 and 0.11µrad) by the proposed approach even in 169 beamlets, which also has high tolerance for defocus errors. This work could provide valuable reference on the practical implementation of high-power, phase-locked fiber laser array systems.

Generation of optical vortex lattices by a coherent beam combining system.

Owing to the unique features in intensity and phase structures, optical vortex lattices (OVLs) have attracted intensive attention and promoted various applications. However, the power scaling of OVLs always presents a critical challenge. Here we take advantage of the brightness enhancement of coherent beam combining (CBC) technology and propose an architecture for creating OVLs based on the CBC system. In the experiment, by utilizing the stochastic parallel gradient descent algorithm, the dynamic phase noises were compensated. The desired piston phase shifting of each element for tailoring the structured wavefront was implemented by the liquid crystal. When the system in a closed loop, hexagonal close-packed OVL consists of spatially distributed orbital angular momentum, beams can be generated in the far-field. This work is an important step toward future implementation of high-power structured light beams.

Switching the orbital angular momentum state of light with mode sorting assisted coherent laser array system.

Light beams carrying orbital angular momentum (OAM) have important implications for future classical and quantum systems. In many applications, controlled switching of the OAM state at high speed is crucial, while accelerating the switching rate presents a long-standing challenge. Here we present a method for flexibly switching the OAM state of light based on a coherent laser array system. In the system, the output structured light beam is tailored by the coherent combination of array elements. By employing an OAM mode sorting assisted phase control subsystem, which continuously performs the optimization algorithm, the dynamic wavefront distortion of the combined OAM beam could be compensated. Meanwhile, our approach allows one to achieve fast states switching of the combined OAM beam via programming the cost function of the algorithm. The results of Monte-Carlo simulations demonstrate the feasibility of the proposed method, and the mode purity and power scaling potential of the controllably generated OAM beam are discussed. This theoretical work could be beneficial to the future implementation of rapidly switchable OAM beams at practical output power.

Comprehensive investigation on the power scaling of a tapered Yb-doped fiber-based monolithic linearly polarized high-peak-power near-transform-limited nanosecond fiber laser.

An all-fiberized linearly polarized nanosecond master oscillator power amplifier based on polarization-maintaining large-mode-area Yb-doped tapered double cladding fiber (T-DCF) is comprehensively investigated. Firstly, excellent performance of the Yb-doped T-DCF for suppressing nonlinear effects, including stimulated Brillouin scattering (SBS) effect and spectral broadening effects, is experimentally demonstrated and qualitatively analyzed. An SBS-free average output power of 8.8 W is obtained under pulse duration of 3.8 ns and repetition frequency of 80 kHz, with peak power of ∼30 kW, pulse energy of 110 µJ and nearly transform-limited linewidth of < 283.8 MHz respectively. The polarization extinction ratio is > 16 dB and near-diffraction-limited beam quality with M2 factor of 1.2 is maintained at the maximal output power. Moreover, the discussion on the optimization of the system for further power scaling is carried out based a nonlinear dynamic model that is capable of simultaneously evaluating the time-domain and frequency-domain evolution properties of the narrow-linewidth linearly-polarized pulsed laser, and meaningful conclusion is obtained.